This application claims priority of European Patent Application No. 99610023.6 filed Mar. 29, 1999 in the European Patent Office.
The present invention relates to medical devices and more particularly to a guidewire for vascular procedures.
Medical guidewires for vascular procedures, such as angioplasty procedures, diagnostic and interventional procedures, percutaneous access procedures, or radiological and neuroradiological procedures in general, traditionally comprise an elongated core element with one or more tapered sections near the distal end thereof and a flexible helical coil disposed about the distal portion of the core element. The distal extremity of the core element or a separate safety ribbon which is secured to the distal extremity of the core element extends through the flexible coil and is secured to the distal end member of the guidewire, which is a rounded member at the distal end of the helical coil. Torquing means are provided on the proximal end of the core element to rotate and steer the guidewire while it is being advanced through a patient""s vascular system.
The physician views the progress on a screen and causes the distal end of the guidewire to enter and follow tortuous vascular vessels from the entry site through the various vascular branches to the target site, by pushing and rotating the proximal end of the guidewire outside of the patient. In connection with the advancement of the guidewire once the guidewire has been positioned at the desired site, a wide variety of medical devices may be directed to the target site along the guidewire by simply sliding the device over the guidewire and advance the device to the distal end of the guidewire. A typical medical device is a catheter; very often a catheter and the guidewire are introduced in a common procedure where the guidewire is advanced a distance in front of the catheter, then the catheter is advanced over the guidewire, followed by a further advancement of the guidewire, and so forth. Following placement of the catheter or other device, the guidewire can be removed if desired.
The flexible coil acts as a protective measure of a suitably large diameter, hindering the guidewire core in damaging the vascular wall. The above mentioned guidewire is known from U.S. Pat. No. 4,619,274 to Morrison whose guidewire has a progressively attenuated diameter. An elongated core element extends from the proximal to the distal ends of the guidewire and has a decreasing cross sectional area in a direction towards the distal end member. A coil is carried by and secured to said core element and has proximal and distal ends. The coil has a diameter which decreases in a direction towards the distal end. The coil is formed of a single helical wound wire which has a diameter which decreases from one end to the other end with the larger diameter beginning in a region closer to the proximal end and the smaller diameter wire ending in a region closer to the distal end.
U.S. Pat. No. 5,001,825 to Halpern describes a fabrication process for a guidewire core where a solid metal wire is drawn down in several stages to have a stepwise decreasing diameter towards the distal end. The core is surrounded by a flexible coil having an outer diameter which decreases near the distal end. The coil consists of a single helical wound wire having a constant cross sectional area. The core element transfers the torque to the distal area of the guidewire, but the core element also restricts the flexibility of the guidewire. When the core element is given a very small diameter in its distal area in order to improve the flexibility, it loses the ability to transfer the torque.
It is an object of the present invention to provide a guidewire which in its distal area is highly flexible and yet capable of transferring torques applied to the proximal end of the guidewire to the distal end of the guidewire in a very precise manner even when the guidewire follows a loop-shaped course.
In view of this, the guidewire according to the present invention comprises a distal end member and a shaft portion extending in a longitudinal direction from a proximal end towards the distal end member, and a single helical wound wire extending from a position at the shaft portion to the distal end member. The inventive guidewire is characterized in that the single helical wound wire is ribbon-shaped and has a pitch angle in the range of 35xc2x0-76xc2x0.
When, according to the invention, the flexible coil in the distal end of the guidewire is ribbon-shaped and wound with a pitch angle in the specified range, the wound wire transfers torque, and also force components directed in the axial direction of the guidewire, to the distal end thereof. The guidewire surprisingly maintains its capabilities for transferring torque when it follows a tortuous path involving two or more loops. The torque is transferred all the way to the distal end member or tip of the guidewire, meaning that the distal end member can be very precisely steered from the proximal end. The widest cross sectional dimension, the breadth, of the ribbon-shaped wire is directed in the longitudinal direction of the guidewire. It is preferred that the ribbon-shaped wire has rounded edges.
In a preferred embodiment, along a distance of at least 10 cm from the distal end member said ribbon-shaped wire is the primary or the sole torque-transferring means between the shaft portion and the distal end member. Because the torque is transferred through the ribbon-shaped wire the central core can be given very feeble dimensions, thus increasing the flexibility of the distal portion, or it can be completely left out by making at least the most distal 10 cm of the guidewire without a torque-transferring solid metallic core inside said ribbon-shaped wire. If desired there can be a safety ribbon inside the ribbon-shaped wire, connecting the rounded distal end member with a more proximal shaft portion, but such a safety ribbon will normally not be required.
Due to the very high flexibility, pushability and torquability and the ability of the guidewire to maintain each of these three characteristics even when set in a very tortuous pattern involving two or more tight loops the guidewire can be of use in very small and distant vessels. In order to further enhance use of the guidewire in vessels with small lumen the ribbonshaped wire can have a smaller outer diameter at the distal end than at said position on the shaft portion.
If the ribbon-shaped wire is secured to the shaft, which can, for example, be of traditional type with a core member or can be another ribbon-shaped wire of larger dimensions, such as by soldering or welding the proximal end of the wire onto the shaft the guidewire can be prone to kinking at the transition between the wire and the remainder of the shaft. With a view to avoiding this, the helical wound wire preferably extends into the shaft portion towards the proximal end, and even more preferably it extends along a guidewire length at least in the range of 20-50 cm from the distal end. The additional stiffness caused by the attachment of the wire is less disturbing the farther it occurs from the distal end of the guidewire. It is possible to let the ribbon-shaped wire extend to a position at the proximal end of the guidewire, so that is spans the entire guidewire.
In the preferred embodiment the guidewire is made without a solid or hollow metallic core inside the at least one coil. By dispensing with the metallic core the flexibility of the guidewire is increased, and the manufacturing of the guidewire is simplified.
In an embodiment the radial thickness of the ribbon-shaped wire is larger in the proximal portion of the guidewire than in the distal portion thereof. Such a variation of the cross-sectional shape can be the result of grinding of a helical wound wire on its outside with the purpose of reducing the diameter of the helical wound wire in its distal portion. The reduced cross-sectional area greatly increases the bending flexibility of the helical wound wire without sacrificing its ability to transfer torque.
The present invention also relates to a method of manufacturing a guidewire, wherein a guidewire body is provided, said body comprising at single helical wound, ribbon-shaped wire having a pitch angle in the range of 35xc2x0-76xc2x0, wherein an elongate distal guidewire portion of said guidewire body is subjected to grinding reducing the outer diameter of said distal guidewire portion in relation to a proximal portion of the guidewire. Grinding is an advantageous manner of manufacturing the above mentioned guidewires because it is very easy to adapt the grinding process to the specific guidewire to be produced, and a wide variety of guidewires can be pre-manufactured as wound guidewire bodies having an even outer diameter along their entire length. When the specific use of the guidewire is specified, such as a guidewire for accessing a kidney in an adult via the femoral route, which requires a guidewire having a relatively long portion with the full diameter and a relatively short portion with a quickly reduced diameter, or a guidewire for neuroradiological use via the femoral route, which requires a gentle reduction in diameter over a relatively long distance and a long and soft distal portion, it is a simple matter to adjust the grinding process to the desired guidewire.
The method can be adjusted to grind the elongate distal portion of the guide wire to have a substantially continuously diminishing outer diameter which results in a gradual increase of bending flexibility of the guidewire. It is further possible to adjust the method to grind the elongate distal portion of the guide wire to have a substantially stepwise diminishing outer diameter which is often preferable in case of very long distal portions.
Further, the method can be so that elongate distal portions of the guide wire are ground to have areas with diminishing outer diameters mixed with areas having substantially constant outer diameters.